It is of course well known that Ziegler-Natta catalysts used for olefin polymerization, can be deactivated when it is desired to either "kill" the polymerization reaction or to control the activity of the catalysts. Representative patents which disclose and claim various techniques include for example U.S. Pat. No. 4,430,488; U.S. Pat. No. 4,105,609; U.S. Pat. No. 3,876,600; U.S. Pat. No. 3,708,465; and U.S. Pat. No. 3,520,866.
More recently, U.S. Pat. No. 4,649,128 issued to Rekers et al on Mar. 10, 1987 discloses a method for controlling the activity of, or deactivating a transition element olefin polymerization catalyst by contacting the catalyst with a deactivating polymer comprising a homopolymer of an unsaturated polar organic compound or a copolymer of an alpha-olefin and an unsaturated polar organic compound.
As is known olefin polymers can be produced in a solution, slurry or gas phase polymerization system. The ability to terminate or slow down an olefin polymerization reaction using a Ziegler-Natta catalyst system is particularly desirable for a gas phase system such as a fluidized bed polymerization system. In general, the equipment for producing olefin polymers such as ethylene copolymers in a fluidized bed system include a conventional polymerization reactor, one or more heat exchangers, one or more compressors, a discharge system and piping connected to the various equipment.
Unfortunately however, during normal operations, undesirable polymer deposits tend to foul the heating exchangers, piping and equipment utilized. For example, during normal operations, the surfaces of the tubes of the heat exchanger or cooler tend to foul with undesirable polymer deposits. These deposits tend to reduce the heat exchanger capability in cooling the recycled gas which removes the heat of reaction, and also it increases the pressure drop across the heat exchanger, which adds to the load on the cycle gas compressor. Because of increasing pressure drop and/or decreased heat exchanger capability the reactor must be shut down within a short time for cleaning.
To alleviate this particular problem, it has been disclosed in U.S. Pat. No. 5,037,905 that polymer build-up in a heat exchanger during the gas phase polymerization of alpha-olefins can be inhibited by introducing para ethyl ethoxy benzoate (PEEB) upstream of the heat exchanger.
The inhibitor is generally employed in the range of about 5-20 pounds of PEEB per million pounds of polymerized alpha-olefins.
In the case of slurry or solution polymerization systems a kill reagent is also necessary to either control or terminate a run away reaction.
It has now been found that certain 1,2 diether organic compounds are eminently suitable for either completely terminating a Ziegler-Natta olefin polymerization reaction or alternatively the reaction can be slowed down if desired, moderating or eliminating the activity of the catalyst. Advantageously, this can be accomplished with very low levels of the deactivator reagents of the present invention.